Dimethyl sulfate hazard

The workup for such reactions involves neutralization and concomitant generation of salts such as NaCl, Na2S04, and (NH4)2S04. The ehmination of such waste streams and a reduction in the dependence on the use of hazardous chemicals, such as phosgene, dimethyl sulfate, peracids, sodium azide, halogens, and HF, are primary goals in green chemistry. 

Methyl ethers are usually prepared by some variant of the Williamson ether synthesis in which an alcohol reacts with either iodomethane, dimethyl sulfate, or methyl triflate (HAZARD) in the presence of a suitable base. A word of caution dimethyl sulfate and methyl triflate, tike all powerful alkylating agents, are potentially carcinogenic and therefore should only be handled in a well-ventilated fume hood. For the 0-methylation of phenols (pKa 10) a comparatively weak base such as potassium carbonate in conjunction with dimethyl sulfate is sufficient,193 whereas simple aliphatic alcohols require stronger bases such as sodium hydride [Scheme 4.111]22 or lithium hexamethyldisilazide [Scheme 4.112].203 The latter transformation is notable for the fact that 0-methyiation was accomplished without competing elimination. 

This methylation reaction can be more economically accomplished using sodium hydroxide and dimethyl sulfate in aqueous solution (see Procedure B). The method described here avoids the use of the hazardous chemical dimethyl sulfate and gives comparable yields, employing a simple procedure. 

Dimethyl Sulfate 182 240 Data not available Data not available Water, foam, carbon dioxide, or dry chemical Not pertinent Not pertinent 370 Slow, non-hazardous reaction ... 

Health hazard degree four (4), the most dangerous, is characterized by such chemicals as cyanogen, dimethyl sulfate, methyl parathion in xylene, beryllium and hydrogen flouride. 

Some starting materials may not be tested for compliance because of the hazards involved (e.g., phosphorus pentachloride and dimethyl sulfate). This is acceptable when a batch certificate of analysis is available from the vendor and when there is a reason based on safety or other valid considerations. 

Safety. Alkylated products in themselves are not as a rule hazardous, although some of them, such as tetraethyllead, are toxic. However, some alkylating agents must be handled with considerable care, e.g., dimethyl sulfate. Among the catalysts, hydrogen fluoride is very toxic and hazardous, but the conditions for its safe handling have been worked out (see HF Alkylation), and consequently it may be employed without undue risk. 

Noteworthy is the fact that these reactions produce no hazardous waste. Conversely from tiie methylations with dimethyl sulfate or methylchloride where a base is also used as a reagent resulting in the generation of stoichiometric quantities of inorgartic salts, the reactions of DMC use a catalytic base CO2 does not involve disposal problems and the co-product methanol can be easily recycled for DMC production. Actually, these reactions are of a significant environmental interest they favorably couple safe reaction conditions (c.-f.) to the use of a nontoxic methylating agent in a waste-firee process. 

During the preparation of methyl azide from dimethyl sulfate and sodium azide, an explosion occurred. The same reaction had previously been carried out without incident. Upon investigation, the chemists found that Bretherick s Handbook of Reactive Chemical Hazards reported that this reaction can result in an explosion if the acidity of the solution drops to pH 5. It was surmised that sodium hydroxide, which was added to maintain the pH above 7, was not added at a sufficient rate to keep the solution at the required pH. Further steps (visible color indicator) were taken in subsequent preparations to ensure that the pH was maintained in the appropriate range. 

Ability to safely operate pressurized reactions with methyl chloride, a flammable gas reactant, or work with highly hazardous liquid alkylating agents such as dimethyl sulfate, dieth-ylsulfate, or BC... 

NIOSH, Dimethyl Sulfate, NIOSH Pocket Guide to Chemical Hazards, http //www.cdc.gov/niosh/npg/npgd0229.html, (accessed Nov 2014). 

The easiest organic azide and smallest member of azidomethanes, CH3N3, was first prepared by O. Dimroth in 1905 by simple methylation of sodium azide with dimethyl sulfate. Methyl azide has been proven to be more explosive than originally reported (same accounts for ethyl azide). The much more hazardous diazidomethane, CH2(N3)2 and triazidomethane, CH(N3)3, are accessible by rather time-consuming slow reactions of dichloro/dibromomethane and tribromomethane with a polymeric ammonium azide reagent. Several reports on the potential risk when working with azides in dichlorometh-ane exist, and are attributed to the potential formation of diazidomethane (please see appropriate references cited in ref. °). 

The reaction of trialkyloxonium salts with carboxylic acids is a mild, general esterification procedure that does not require the use of more hazardous reagents such as Hexamethylphospho-lie Triamide-Thionyl Chloride, lodomethane. Dimethyl Sulfate, 3-Methyl-l-p-tolyltriazene, or Diazomethane. The reaction proceeds smoothly with sterically hindered acids, as well as with acids containing various functional groups such as amides or nitriles (eq 10). ... 

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